1. Field of the Invention
This invention pertains to footwear in general, and in particular, to footwear with lights that flash to enhance the visibility of the wearer.
2. Description of the Related Art
It has long been known in the field of footwear to incorporate lighting devices, usually electrical in nature, into shoes, boots, sandals and the like for various reasons, e.g., to permit the wearer to see or be seen in reduced light situations, or to provide special effects during certain entertainment events.
A simple implementation of this type of footwear typically includes a light source, e.g., an incandescent bulb, a neon tube, or a light emitting diode ("LED") , a portable power supply, such as a battery, a manually operated on-off switch, and an electrical circuit connecting the three in series, all located in the footwear, typically within the sole and/or heel structures. Examples of these in the patent art may be found in the sandal of B. Arias et al. in U.S. Pat. No. 2,931,893, in the high heel shoe of A. McCormick in U.S. Pat. No. 4,253,253, and in the dress shoe heel described by W. Pahde in German Patent Application 3343-897-A.
More complex lighted footwear efforts have been directed to switching the lighting circuit on and off in association with the presence or absence of the wearer's foot in the shoe, or by the contact of the wearer's foot with the ground, e.g., during walking or running. Examples of the former in which the lighting circuit is switched on when the wearer's foot is inserted into the shoe include the houseshoe in U.S. Pat. No. 3,008,038 to M. Dickens et al., and the high heel described in Dutch Patent Application No. 8,005,050 by J. de Nijs, et al. The latter reference also includes means for automatically deactivating the lighting circuit under conditions of high ambient light.
Examples of footwear lighting circuits activated by a switch disposed in the sole of the shoe and actuated by pressure exerted on it by the underside of the wearer's foot in contacting the ground may be found in: U.S. Pat. No. 3,800,133 to H. Duval; U.S. Pat. No. 4,014,115 to R. Reichert; U.S. Pat. No. 5,052,131 to P. Rondini; and, Belgian Patent Application No. 570,614 to E. Abramovitch et al. A more elaborate example involving a pneumatically actuated switch is described in European Patent Application No. 335,467A by A. Heister, et al.
Examples of footwear lighting circuits activated by a switch disposed in the sole of the shoe and actuated by pressure exerted on it by the ground when the shoe contacts the ground may be found in: U.S. Pat. No. 1,933,243 to J. De Merolis et al; U.S. Pat. No. 3,070,907 to J. Rocco; U.S. Pat. No. 4,128,861 to A. Pelengaris; U.S. Pat. No. 4,130,951 to A. Powell; and, British Patent No. 444,392 to J. Jordan.
Examples of footwear containing lighting circuits activated by the angular position of the footwear include those found in U.S. Pat. Nos. 3,893,247 and 4,158,922, both to A. Dana, III, and U.S. Pat. No. 4,848,009 to N. Rodgers.
Each of the three examples in the latter group involves a "tilt switch," i.e., a mercury switch, to sense the angular position of the shoe with respect to the gravity gradient and to activate the circuit at a particular attitude. In the first two of these, the lights are on so long as the shoe is in a given attitude, and off in a second attitude, and both references require a master switch to deactivate their respective circuits unconditionally of the footwear's angular position. The last reference incorporates an electronic timing and "latching" circuit that turns the lighting circuit off a predetermined period of time after the switch is closed, and maintains it in the off state until the switch is first opened, then closed again. Thus, in each of these latter examples, the on-off condition of the light circuit is a function of the angular position of the footwear, and in particular, that of the tilt switch, relative to the gravity gradient, and is independent of any translational movement of the footwear or its position relative to the ground surface.
Each of the above-described examples of the relevant art is subject to certain shortcomings. Those that are "on" continuously tend to exhaust their batteries more quickly than those that are on only intermittently.
Those that are "on" only when the foot is in contact with the ground or in a certain angular position and otherwise "off" are not as effective as they might be for two reasons. First, the footwear is more likely to be obscured by, e.g., grass or uneven terrain when the foot is at ground level than when it is above the ground, and generally, the higher the light is above the ground, the further away it can be seen.
Secondly, in normal walking or running activities, the footwear, and hence, the light sources, are typically static, or unmoving, when the footwear is on the ground, and moving only when the footwear is above the ground. Two psychophysical phenomena act to ensure that the moving lights will be more readily seen than the static ones: First, in a static field, a moving object is more easily detected by the eye than a static one. Second, under appropriate lighting conditions, a moving point source of light is perceived, due to the phenomenon of "persistence," by the human eye (and some cameras) as a large, elongated streak of light "painted" on the retina of the eye by the point source, rather than as a small, moving point of light.
The present invention overcomes the limitations of the art described above and enhances the visibility of the wearer by the provision of a simple, economical and reliable design for footwear containing a lighting system that is "off" when the wearer's foot is contact with the ground, and unmoving, thereby conserving battery life, and "on" when the wearer's foot is off the ground, and usually moving, thereby enhancing the wearer's visibility for the reasons given above.